live dsc upgrade from 2.0 to 2.1 behind the scenes

[Park Wu <pa...@yahoo.com.INVALID>]

Hi, folks: I am planning to upgrade our production from dsc 2.0.16 to 2.1.18 for 2 DC (20 nodes each, 600GB per node). Few questions:1), what happen when doing rolling upgrade? Let''s say we upgrade only one node to new version, before upgrade sstable, the data coming in will stay in the node and not be able to stream to other nodes?2), What if I have very active writes? how much data it can hold until it sees other nodes with new version so it can stream?3), Should I upgrade sstable when all nodes in one DC upgraded? or wait until all 2 DC upgraded?4), any idea or experience how long it will take to upgrade sstable for 600 GB data on each node?5), what is the max time I can take for rolling upgrade on each DC?6), I was doing a test with 3-nodes cluster, one node with 2.1.18, other two are 2.0.16. I got a warning on the node with newer version when I tried to create keyspace and insert some sample data:"Warning: schema version mismatch detected, which might be caused by DOWN nodes; if this is not the case, check the schema versions of your nodes in system.local and system.peers. OperationTimedOut: errors={}, last_host=xxx"But data upserted successfully, even not be seen on other nodes. Any suggestion?Great thanks for any help or comments!- Park